Element spots in Ap- and HgMn-stars from current-driven diffusion

TL;DR

This paper investigates how electric current-driven diffusion can create chemical spots on the surfaces of Ap- and HgMn-stars, potentially explaining observed surface inhomogeneities in these stars.

Contribution

It introduces a diffusion mechanism driven by electric currents that can form chemical spots even in weak magnetic fields, expanding understanding of stellar surface chemistry.

Findings

Electric current-driven diffusion can produce chemical spots.

The mechanism is effective even with weak magnetic fields.

It may explain surface inhomogeneities in HgMn- and Ap-stars.

Abstract

The stars of the middle main sequence often have spot-like chemical structures at their surfaces. We consider the diffusion process caused by electric currents that can lead to the formation of such chemical spots. Diffusion is considered using the partial momentum equations derived by the Chapman-Enskog method. We argue that diffusion caused by electric currents can substantially change the surface chemistry of stars and form spotted chemical structures even in a relatively weak magnetic field. The considered mechanism can be responsible for a formation of element spots in HgMn- and Ap-stars.